Mao's declaration condemned the Chinese Communist Party (CCP), the army and the government for having been infiltrated by "representatives of the bourgeoisie" and "counter-revolutionary revisionists."
Hundreds of thousands of people were killed as the country fell into what Dikotter describes as civil war, with different Red Guard and People's Liberation Army (PLA) factions fighting each other, and millions more were displaced and traumatized as society broke down around them.
Timeline of the Cultural Revolution
The great leap backward
Following the unmitigated disaster of the Great Leap Forward — in which tens of millions of ordinary Chinese died as a result of Mao's policies — the Chairman was at perhaps his most vulnerable point since the end of the Second World War.
With his May 16 declaration, Mao sought to unleash the power of the people against his enemies in government.
What began in the universities of Beijing soon spread to wider society, with Mao personally writing a big-character poster entitled "Bombard the Headquarters" calling for an attack on the "command center of counter-revolution."
"He pretty much asked the people to attack the Party, which we've never seen before or since," says Dikotter.
"Stalin, Pol Pot, Kim Jong Un, none of them would ever think of asking ordinary people to attack the very machinery they themselves built up."
On August 18, 1966, more than a million Red Guards gathered from all over the country in Beijing's Tiananmen Square. At the rally, Mao loyalist and defense chief Lin Biao told those assembled to attack "counter revolutionaries" and destroy the Four Olds of customs, culture, habits and ideas.
"There were endless numbers of people, who when they are asked by Mao to criticize Party members, simply can't wait," says Dikotter.
"There were so many pent up grievances caused by years of Communist rule. All those who suffered in the Great Leap Forward, workers in factories living in appalling conditions, victims of early campaigns and purges, and they really do denounce many of these Party leaders."
Throughout this period, Dikotter says, Mao was "trying to create chaos in order to keep pretty much everyone on their toes."
Even those who hated Communism, and knew they were being manipulated by Mao, embraced the opportunity to attack local cadres and Party officials.
Torture and suffering
Party officials were by no means the only ones targeted by Red Guards and the newly empowered citizenry.
Thousands of ordinary people — denounced as class enemies and counter revolutionaries — were abused, tortured and killed.
Many were forced into "cowsheds", makeshift detention centers in which they were forced to perform manual labor and recite Maoist tracts and were regularly subject to beatings.
"After a few months in the cowshed, I could feel my emotions being dulled and my thoughts growing more stupid by the day," writes Peking University professor Ji Xianlin in his memoir "The Cowshed
His experiences during that time were a "dizzying descent into hell," Ji writes.
But they were not uncommon. Ji and other, sometimes very elderly, professors and teachers were beaten, spat upon and tortured in rallies and criticism sessions that could last hours.
In Daxing county, on the outskirts of Beijing, cadres ordered the extermination of all landlords and "other bad elements," Dikotter recounts.
"Some were clubbed to death, others stabbed with chaff cutters or strangled with wire. Several were electrocuted. Children were hung by their feet and whipped."
More than 300 people were killed, with their bodies thrown into disused wells and mass graves.
As the country plunged into chaos, Mao's fervor increased.
"It's a game that Mao is playing," Dikotter says. "He incites students to attack teachers, then unleashes the population on the Party itself, then asks the army to step in, before you know it people are literally fighting each other."
According to Dikotter, Mao created a frenzied cycle "where people are endlessly trying to prove their allegiance to the Chairman."
From Mao's perspective, the Cultural Revolution was a great success. Insubordinate Party higher-ups were replaced by his allies, particularly the so-called Gang of Four, led by Mao's wife Jiang Qing.
Could it have been stopped?
"There were at least two points where (Party officials) could have done something," Dikotter says.
Following the Great Leap Forward, "Mao's star is very much at its lowest, at that point they could have hemmed him in, but the Chairman manages to very astutely talk his way out of that predicament."
By taking partial blame for the disaster, Mao forced other high-ranking officials to admit their own complicity, undermining their authority and strengthening his position.
"The second point is probably in February 1967 when several veteran marshals openly rebel against the Cultural Revolution group presided over by Madame Mao," Dikotter says.
"Mao realizes that if these veteran marshals push their criticisms through, it would have dire consequences and he might end up being at the losing end."
But Mao, the "master of corridor politics" was able to keep Premier Zhou Enlai and other key officials on side, and eventually the generals were denounced and purged.
Ultimately, any attempt to stop the Cultural Revolution was hamstrung by the same reason today's China has been unable to properly reckon with its history: the primacy of Mao.
"When Kruschev started de-Stalinization he knew full well you can drag Stalin's body out of the mausoleum because there is another body there, Lenin's," says Dikotter.
"In the case of China this would be impossible, the entire history of the Chinese Communist Party revolves around the personality of Mao ... which is why the Party will never, ever promote a critical examination of its own history."
While moves were taken to contain the chaos and return the country to something approaching normality in the early 70s, it was not until Mao's death, on September 9, 1976, that the Cultural Revolution truly ended.
Backed by the army, Mao's successor Hua Guofeng had the Gang of Four arrested, and moderates, including Deng Xiaoping, were welcomed back into the fold.
By 1978, Deng would be paramount leader, as he and his supporters oversaw the reversal of Cultural Revolution policies and the official opening up of China's economy.
While Deng is often given credit for turning China from a collectivist, Communist economy into the powerhouse it would become, according to Dikotter, Deng's reforms were a reflection of those forced upon the country from the bottom up, by a populace alienated to and despairing of Communism.
"For the vast majority of the people in the countryside, the credibility of the Communist Party was damaged already during the Great Leap Forward," he says.
"When the organization of the Party is damaged by the Cultural Revolution, there's very little left in the countryside to believe in."
Throughout the country, people began setting up markets and exchanges. They "undermine the planned economy and force Deng Xiaoping to abandon it."
This economic reform, driven by the very people who were most abused by Communist rule, would see millions of Chinese lifted from poverty and change the country forever.